1. Technical Field
The present invention relates to a printed circuit board for an optical waveguide and a method of manufacturing the same.
2. Description of the Related Art
Recently, there has been a rapid increase in demand for an optical substrate which includes wiring for transmitting electrical and optical signals to mobile or network appliances which require high-speed data transmission.
Generally, an optical substrate is made of a polymer having low light transmittance, and includes a square-section core having a width in which signals are really transmitted and a thickness of 50 μm and a clad covering the core. The square-section core is generally fabricated through a photo-etching process.
In relation to this, a conventional method of manufacturing a printed circuit board for an optical waveguide will be described as follows with reference to FIGS. 1A, 1B and 1C.
First, a soft substrate comprising a copper foil 11 and a polyimide layer 12 is prepared, and a lower clad layer 13 and a core layer 14 are sequentially formed on the polyimide layer 12 of the soft substrate (refer to FIG. 1A).
Subsequently, the core layer 14 is patterned through a photo-etching process to form cores 14a (refer to FIG. 1B).
Finally, an upper clad layer 15 is formed on the lower clad layer 13 on which the cores 14a are formed, thus completing a printed circuit board for an optical waveguide (refer to FIG. 1C).
According to the above conventional method, there is a problem in that the entire work size substrate is coated with a core material to form a core layer 14, and then the core layer 14 is patterned through exposure/development to form cores 14a, so that a very large amount of the core material is removed compared to the amount of the really necessary core 14a, thereby increasing the material cost outlay.
Furthermore, there is a problem in that, although lower and upper clad layers are sufficient to cover cores 14a to such a degree that the optical signal transmission of the cores 14a is easily achieved, a clad material is entirely applied on the substrate, so that the clad material is excessively used.
In particular, considering that raw materials of optical substrates are high-priced, methods of economically and efficiently manufacturing an optical substrate are keenly required.